1. Field of the Invention
The present invention relates to an electronic circuit device including a plane antenna such as microstrip patch antenna, and more particularily to an electronic circuit device which is useful where low cost is a requirement.
2. Description of the related Art
Microstrip patch antennas are widely used with mobile radio communication devices utilizing microwaves and have features of low cost and ease of manufacture, as well as low profile and high gain.
Demand is increasing for less expensive, more easily manufactured electronic circuit devices which include plane antennas such as microstrip patch antennas as described above.
FIGS. 1A and 1B illustrate an example of a prior art electronic circuit device which includes a plane antenna used as a discrete component. FIG. 1A is a perspective view and FIG. 1B is a side sectional view. In these Figures, reference numeral 1 denotes an antenna element, 2 an antenna substrate, 3 a printed circuit board, 4 a substrate of printed-circuit board 3, 5 a ground plane, 6 a circuit pattern, 7 discrete components, 8 a microwave transmitting/receiving section, 9 a feed point to the antenna element 1, and 10 a connecting pin.
In FIGS. 1A and 1B, antenna element 1 is made of a conductor and is square, the length of one side measuring about .lambda./2 (.lambda. is a wavelength used) long. It is formed on antenna substrate 2, which is made of a dielectric material, and has a contour larger than the antenna element, thereby constituting a microstrip patch antenna. With printed circuit board 3, ground plane 5 comprising a conductor covers the surface of substrate 4, which comprises of a dielectric material. Circuit pattern 6 is formed on the other side of substrate 4. Circuit pattern 6 has a circuit comprising of a microstrip line and is fixed in its prescribed positions by components 7.
Antenna substrate 2 is mounted on that portion of ground plane 5 which corresponds in position to microwave transmitting/receiving section 8 on circuit pattern 6 by bonding with antenna element 1 turned up. Feed point 9 and microwave transmitting/receiving section 8 are connected by connecting pin 10, which passes through printed-circuit board 3.
FIGS. 2A and 2B illustrate another example of the prior art electronic circuit device, which includes a plane antenna formed integrally with a case for housing an electronic circuit. FIG. 2A is a perspective view and FIG. 2B is a side sectional view. In these Figures, reference numeral 11 designates an antenna conductor plate and 12a package.
In FIGS. 2A and 2B, antenna conductor plate 11 is bonded to the top surface of package 12, which is formed of a dielectric material.
Printed circuit board 3, as in FIGS. 1A and 1B, is mounted on the inner surface of package 12 with circuit pattern 6 turned down. Microwave transmitting/receiving section 8 on circuit pattern 6 and feed point 9 of antenna conductor plate 11 are connected to each other by means of connecting pin 10, which passes through package 12 and printed circuit board 3.
With the prior art electronic circuit device shown in FIGS. 1A and 1B, antenna element 1 and connecting pin 10 are usually soldered together. Thus, a heat-resisting dielectric material such as glass epoxy is used for antenna substrate 2. This makes antenna substrate 2 difficult to manufacture by die molding. Moreover, holes must be bored in antenna substrate 2 and printed circuit board 3, the holes must be aligned with each other and soldering is required. This raises the manufacturing cost.
In the prior art electronic circuit device shown in FIGS. 2A and 2B, the material used for package 12 usually has no heat resistance. Thus, antenna conductor plate 11 and connecting pin 10 have to be connected beforehand by welding or soldering. This gives additional trouble and requires that antenna conductor plate 11 be made thicker. This raises the manufacturing cost.